1. Field of the Invention
The present invention relates to a power semiconductor device.
2. Description of the Background Art
Power semiconductor devices such as an insulated gate bipolar transistor (IGBT) handle a large amount of power, and as a result generate large amount of heat from conduction loss. Accordingly, the temperature of a semiconductor substrate increases greatly, and the temperature varies largely by an on/off operation.
Large temperature rise, temperature change or the like incurs, for example, fatigue of a wire-bonded portion, thus leading to a reduction in power cycle life. Note that the power cycle life is one indication of the reliability of a power semiconductor device, which indicates the life influenced by, for example, peeling of a wire bonding portion due to a temperature change incident to operation.
It is considered that, in a power semiconductor device, the temperature becomes higher in a central portion of the substrate than a peripheral portion of the substrate and the temperature of the entire substrate is increased by the temperature of the central portion of the substrate. Japanese Patent Application Laid-Open No. 06-342876 describes a semiconductor device having a function of detecting the temperature of the central portion of the substrate to prevent thermal fracture due to a temperature rise.
Specifically, in the semiconductor device of Japanese Patent Application Laid-Open No. 06-342876, the empty space is provided in the central portion of a power transistor (corresponding to the central portion of the substrate) formed on the semiconductor substrate, to thereby form a temperature detecting element such as a temperature detecting transistor in the empty space. The power transistor is controlled in accordance with the temperature detected by the temperature detecting element.
However, in the semiconductor device of Japanese Patent Application Laid-Open No. 06-342876, the region in which the temperature detecting element is disposed needs to be secured, which leads to an increase in device size.